VR.WaitForGPU basically means that your frames are taking too long to render. To maintain 90fps, you need to be < or about equal to 12ms per frame (1000ms/s / 90 frames/s = 11.11111). Both your CPU and GPU values are above that. So VR.WaitForGPU is not killing performance - that function is actually the CPU saying that it needs to wait some amount of time for rendering to finish before it can send new data to the GPU. If you want to address this, you need to look at how much you are trying to render each frame and reduce/optimize where possible.
When the headset is active, frame-rate is being locked/synched to 90fps, even if your cpu/gpu could push further. It's a similar principle to having v-sync enabled on a monitor.